1. Field of the Invention
This invention relates to a protective puncture proof material and more particularly to a flexible puncture proof material to protect against accidental injuries from needles, scalpel blades, knives and other sharp pointed instruments.
2. Description of the Related Art
Protection from accidental cuts and punctures is needed in the fields of medicine and law enforcement, and in any occupation where sharp instruments are encountered and where the combination of flexibility and protection against cuts and puncture wounds is needed.
Accidental needle sticks and scalpel blade cuts occur to doctors and nurses, while performing surgery, giving injections, taking blood samples, and administering intravenous liquids. The accidental needle sticks and scalpel blade cuts by themselves are harmful; however, in a medical situation a cut or puncture can also transmit infection either to the patient or to the medical person performing the procedure.
In the past, the main concern was that a surgeon would infect the patient during surgery. This is still a concern and is adequately addressed by using latex gloves. Unfortunately, it is also increasingly crucial to protect surgeons and other medical personnel from infection. A surgeon can contract hepatitis, AIDS, and other diseases, when the blood or body fluid of a patient is transmitted through the skin of the surgeon. It is estimated that the average surgeon has about three cuts or puncture wounds per month, caused by either a hypodermic needle or a scalpel blade. This presents an unacceptable risk factor for surgeons and other medical personnel. Similarly in a law enforcement situation, an assailant wielding a blood stained knife could seriously injure and infect law enforcement personnel.
Conventionally, surgeons and other medical personnel wear sterilized latex gloves, which are thin and flexible enough to enable a surgeon to freely manipulate his fingers, and to utilize his sense of touch. If the latex gloves are not penetrated then the patient and the surgeon are protected from infection; however, latex gloves offer hardly any protection against accidental punctures or cuts, because hypodermic needles and scalpel blades can easily puncture or cut through a latex glove. Even multiple layers of latex gloves, which medical personnel increasingly use to provide additional protection against transmission of infection, offer no protection against accidental punctures or cuts.
It is important to distinguish between cuts and puncture wounds. A cut is typically from the edge of a scalpel blade. A puncture wound can be caused by the point of a scalpel blade or by the point of a hypodermic needle. A scalpel blade is typically about 0.75 inches long with a sharpened edge and with a point about 0.010 inches in diameter. A hypodermic needle can be as small as 0.010 inches in diameter at the point widening to about 0.018 inches in diameter for the shaft of a No. 27 needle. It is much easier to protect against a cut from an edge of a scalpel blade than to protect against a puncture from either a scalpel blade or a hypodermic needle, because a scalpel blade has a wider surface upon which the pressure of the cut is distributed. For example, if the pressure is 2000 grams, then the pressure per square area for a scalpel blade is 2000/(0.75*0.010), assuming the edge of the scalpel blade is the same sharpness as the point of the scalpel blade (0.010 inches) and that the scalpel blade is 0.75 inches long. For a needle with a 0.010 diameter point the same pressure would have a pressure per square area of 2000/(3.14*(0.010/2).sup.2), which is ninety five times greater than the pressure per square area for the edge of a scalpel blade. This factor of approximately one hundred is a key reason that conventional protective gloves fail to offer adequate protection against punctures.
Most accidents in the operating room occur with some significant force. For example, a surgeon turns and is wounded accidently by the point of a needle or scalpel being handed to him by a nurse, or a surgeon while suturing slips and punctures his hand with a needle. Thus, effective protection against punctures should protect against pressures exceeding 2000 grams. This level of protection is well beyond the protection provided by any conventional puncture resistant gloves.
Conventional approaches to providing increased protection beyond latex gloves against cuts and punctures for a surgeon or other medical personnel include: providing a glove with a weave or knit of a material such as Kevlar, nylon, stainless steel or fiberglass; providing reinforced areas such as on glove fingers; placing foam material between two latex gloves; and providing leather on portions of the glove. Some of the materials, such as leather and Kevlar knits provide protection against cuts, but virtually no protection against punctures.
Conventional protective gloves having a weave or knit of a material such as Kevlar, nylon, stainless steel or fiberglass are characterized by U.S. Pat. Nos. 4,526,828, 5,070,540, 4,833,733, 5,087,499, 4,742,578, and 4,779,290. These approaches have fairly effective protection against cuts, because a material such as a Kevlar weave is hard to cut through. However, a shortcoming of all of these approaches is that the weave or knit is simply spread apart by the wedge on a needle or scalpel point to form a passage as the needle or scalpel point is inserted into the material. Making the weave tighter or thicker does not prevent punctures; moreover, a thicker or tighter weave significantly reduces the flexibility of these gloves and their usefulness. As the number of layers or the thickness of the material increases, the ability of a surgeon to freely manipulate his fingers, and to utilize his sense of touch is significantly reduced.
Conventional protective gloves providing reinforced areas are characterized by U.S. Pat. No. 4,865,661, which has woven fiberglass placed at certain areas on the fingers of a glove and U.S. Pat. No. 5,187,815, which has corrugated metal foil in areas to be reinforced. The shortcoming of these approaches is that the reinforced areas have little flexibility so can only be placed on certain areas, which leaves the rest of the glove without the same protection. Also, even woven fiberglass and corrugated metal may be punctured. The point of a #11 blade will easily pass through metal foil 1/2 to 1 mil thick.
The approach of placing foam material between two latex layers is the approach of U.S. Pat. No. 4,901,372, which provides little if any protection against cuts and punctures, because the latex and the foam can be easily cut and punctured.
Providing leather on a glove is an approach that provides some protection to cuts; however, little protection to punctures. Even though the pores of the leather may be smaller than the diameter of a needle, a needle will simply make a hole in the leather as it passes through.
Accordingly, there is a need in the art for a puncture proof material that is flexible and protects against accidental injuries from needles, scalpel blades and other sharp pointed instruments.